Venetian blinds are window coverings composed of a number of horizontal slats arranged in parallel. The vertical space between the slats is slightly less than the width of the slat, allowing the blind to be effectively closed by rotating all the slats to 0 or 180 degrees.

The slats are sometimes connected together using string or cables, which allow the blind to be pulled up or down, eliminating the space between the slats and completely exposing the window.

Other models of venetian blind have the slats fixed in their vertical position, usually by a wooden or vinyl frame. However, to qualify as a venetian blind, one must be able to change the angle of the slats within the frame. If the slats are fixed, this window covering is a shutter.

Venetian blinds were patented (#2223) by John Hampson of New Orleans, Louisiana on August 21, 1841. Some sources credit Hampson with inventing the venetian blind, however this type of blind has been found to be in use hundreds of years before Hampson was born. Hampson’s contribution to the blind was in inventing (or at least patenting) a method for changing the angle of the slats and keeping them synchronized in position.

Early Venetian traders are thought to have brought the blind from Persia to Venice. Freed Venetian slaves, returning to France, are thought to have brought the blind with them. In France the blind is called "Les Persiennes". The blind quickly became popular in England where Victorians were ready to embrace any window covering that didn't involve the usual heavy drape.

Update Aug 18, 2003: the term "slats" can be interchanged with "louvres"